So someone who weighs 173 pounds with a body fat percentage of 17.5% would calculate as follows:

(173)(.175)

= 30.3 lbs. of fat

173 – 30.3

= 142.7 LBM

The accuracy of your LBM number is dependant on the accuracy of your inputs – your weight and your body fat percentage. As body fat percentages can be all over the map based on the methods used, your LBM as an accurate gauge of your fitness level should be taken with a grain of salt.

Use the mirror to make any major judgements about your body, use lean body mass as a progress report for your training program.

The Visible Difference Between Muscle and Fat Weight

You have probably heard the saying, “Muscle weighs more than fat.” This is true. While a pound of muscle weighs the same as a pound of fat, the volume is different. Muscle is denser than fat.

A pound of fat will take up about 18% more space than a pound of muscle. If squeezed into cans, you would need a can 18% bigger to contain the pound of fat.

In addition to volume differences, keep in mind that muscle wraps tightly to the skeletal structure whereas fat hangs loosely. So, all total, you can find two people of the same build and height who weigh the same appearing vastly different based on their lean body mass (LBM).

If your goals are to improve your physical appearance, you should concern yourself more with where your LBM is rather than your bodyweight.

The Importance of Knowing Your LBM?

What if your trip to the scales showed no bodyweight gain in two weeks time? Is it then time to make some big adjustments to your program? Maybe, maybe not.

Your lean body mass number could show that you actually gained muscle (and, necessarily, lost some body fat) which means your program is doing well and you probably wouldn’t want to change a thing.

And, of course, if your bodyweight is moving skyward, you should temper your enthusiasm until you get an accurate estimate of your lean body mass. It may just be body fat you are gaining.

How Much Body Fat Gain Is Acceptable?

On a mass gain program, it isn’t realistic for most people to expect to gain all muscle and no fat. At the most, you want to be gaining at a 1:1 ratio of muscle to fat (1 lb. of muscle for every one pound of fat).

When you switch to a cutting program your focus will be on maintaining your muscle gains while losing the fat.

But… Is this information really necessary for success?

Yes, Yes and YES. Without it you are flying blind when it comes to adjustments. And unless you strike gold right out of the gate, unless you hit on the exact right diet and training program that will quickly take you to desired destination, adjusments will need to be made to maximize your gains.

Just like in bodybuilding, failure is also a necessary experience for growth in our own lives, for if we're never tested to our limits, how will we know how strong we really are? How will we ever grow? - Arnold Schwarzenegger